1. Field of the invention
This invention relates to an automatically operated non-invasive blood pressure measuring and recording system, and more particularly to a system of the type which includes an inflatable cuff for encircling a portion of the human body, usually the arm, means for inflating and deflation the cuff for selectively occluding an arterial vessel, means such as a microphone for detecting flow variations through the vessel as the cuff is delfated, e.g., those variations giving rise to Korotkov sounds identified with the systolic and diastolic pressures, and means for recording arm cuff pressure values in correspondence with the detected flow variations to provide a measurement record.
2. Description of the prior art
In known blood pressure systems the inflation of the pressure cuff is obtained by the operation of either a hand operated pump or an electric pump which is turned off when the desired pressure is reached. Deflation is accomplished with an air escape valve controlled either manually or with a servomechanism, as disclosed in U.S. Pat. No. 3,905,353, to provide a more or less constant rate of pressure drop. These known techniques have not been fully satisfactory, as they either are substantially nonlinear or require complicated means to approach linearity, and as they are affected by ambient conditions and do not provide the reproducability of pressure drop necessary for accurate, repeatable measurements. In addition, such techniques are not readily adaptable to provide a slower linear rate of pressure drop in the particular regions where systolic and diastolic pressures are detected, as suggested for improved measurement accuracy in U.S. Pat. No. 3,814,083 (col. 3, 1. 28-40). Finally, such inflation and deflation techniques do not lend themselves easily to automatic control over a full inflation and deflation cycle, which is desirable from the standpoints of reproducability of measurement and ease of operation.
In addition, known blood pressure systems provide a limited amount of measurement and diagnostic information, either in the form of chart traces of flow variations to be interpreted visually (e.g., U.S. Pat. Nos. 3,811,439, 3,867,926 and 3,878,834), in the form of readouts, either digital or analog, of systolic and diastolic pressures (e.g., U.S. Pat. Nos. 3,085,567, 3,396,405, 3,905,354, 3,623,476 and 3,500,822), or in the form of aural signals to be interpreted traditionally by a physician for the onset and disappearance of Korotkov sounds. Known systems heretofore have not provided multiple sources of information simply and easily, and have not included any arrangement permitting a diagnosis of the action of the artery,e.g., for detection of murmurs and the like, in connection with the blood pressure measurement.
Finally, known automatic blood pressure systems seeking to provide a high degree of automation have been complicated and expensive, and accordingly have failed to realize the potential economies of use by inexperienced or untrained operators.